Posted by: akueddy ® 03/17/2007, 19:24:13 Author Profile eMail author Edit

Hi , i wanna ask about lead acid battery, ii know now the difference between wet and vrla(gel/AGM) types, starter and deep cycle types. I want to design a powered wheel barrow(slow moving,using12V 70Ah battery,cheap ), and its not going to be use regularly. maybe im using it for about 3-4 months in a year. What type of battery would be suitable? For battery capacity,basically if you have a 12V 70Ah battery,usually manufacturer says its for a 20h basis which means, this battery(12V 70Ah) can provide 3.5amps for 20hours, just like the graph show in the link: https://www.battery-oem.com/tech/battery-size.htm this is ok, cause theres a graph,which is easy for me to understand, but : can somebody explain to me how does the "constant current/power discharge characteristics" work? i just want to know aproximately how long will the battery last from the table given, if the battery capacity Ah=current required by motor. Modified by akueddy at Sun, Mar 18, 2007, 20:25:56

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Re: battery question
Re: battery question -- akueddy	Post Reply	Top of thread	Forum

Posted by: Bruiser ® 03/19/2007, 21:58:07 Author Profile eMail author Edit

The table shows cell voltage (multiply it by 6 to get a meaningful figure) and the power or current (almost the same thing) that can be supplied from a full battery (13.8 => 2.3 volts per cell) before getting 'flat'. Various levels of flat are shown. I don't like going below 1.8 - this affects the cycle life a lot. Easiest way, work out how much current you need and look it up. For example, if you need 50A, the table shows you can only do it for 30 minutes, and you'll get down to 1.75 vpc (10.5V). Note that if you work in power (volts x amps) the current will increase over time as the battery voltage falls. Better to work in amps and be a bit careful about how low you go.

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